You don't understand. I'll try to explain.
The number .0001 is not a finite number. There are numbers below and above that number but when the reporting went from fractions, (1/8), to decimals the limited the posts to .0001 (four places), but trades take place below that and above that.
So you think if you place an order at .0001 you should buy, but not so if the ask is .00019, (5 places) so if you put in an order to buy at .0002 you should fill, providing that shares are available.